EP2804883A1

EP2804883A1 - Compact, lightfast polyurethane moulded parts

Info

Publication number: EP2804883A1
Application number: EP13700230.9A
Authority: EP
Inventors: Birgit Meyer Zu Berstenhorst; Reinhard Halpaap; Norbert Eisen; Uwe Pfeuffer; Gregor MURLOWSKI
Original assignee: Bayer Intellectual Property GmbH
Current assignee: Covestro Deutschland AG
Priority date: 2012-01-17
Filing date: 2013-01-15
Publication date: 2014-11-26
Anticipated expiration: 2033-01-15
Also published as: BR112014017086A2; BR112014017086A8; EP2804883B1; ES2608336T3; US20140378641A1; WO2013107722A1

Abstract

The invention relates to compact, lightfast polyurethane moulded parts which consist of isocyanates, polyols and chain extenders and/or cross-linking agents, as well as to the use of same.

Description

Compact, lightfast polyurethane molded parts

The invention relates to compact, lightfast polyurethane moldings of isocyanates, polyols and chain extenders and / or crosslinkers and their use.

Polyurethanes (PUR) based on isocyanates with aromatically bonded NCO groups are known to discolor under the action of light. This is a problem in outdoor or under light exposed interior parts. For the production of light-resistant moldings therefore a surface with appropriate properties is required.

For the preparation of polyurethanes with high light resistance usually aliphatically bound isocyanates are used. A use of such isocyanates for producing light-resistant PUR is described in EP-B 0379246. Here lightfast covering skins, e.g. made for use on instrument panels. It is possible to produce compact and foamed aliphatic skins.

Particularly in applications such as in the automotive interior or in applications in which polyurethane is used as a decorative layer, often compact, insensitive, as "unbreakable" systems (systems that are not destroyed under various influences) are often needed.These should have a Shore A hardness of at least 70, preferably of at least 75. In the production of such polyurethanes from polyol and polyisocyanate should also be easy to use industrial hygiene polyisocyanates used.

Aliphatic isocyanates are known to be significantly less reactive than aromatic, which is why significantly more energy must be added to the reaction. Thus, tool temperatures of 70-90 ° C are often required to start the reaction at all and to harden. Thus, in the systems described so far, such as e.g. from WO 2004/000905, EP-B 0379246, EP-A 0929586 are known, aliphatic polyisocyanates with a high proportion of monomeric diisocyanate used, so that by a strongly exothermic reaction with formation of a high proportion of urethane groups sufficient curing can take place. Curing of these systems can only be achieved by special catalysis.

Furthermore, more and more emphasis is placed on safety in production. It is desirable to have to handle as few hazardous substances, which includes both health and economic aspects, since the safety must be guaranteed by additional suction, enclosures, etc. Therefore, from a working hygiene point of view low-monomer polyisocyanates are preferable to the monomeric diisocyanates. Monomeric aliphatic diisocyanates are generally classified as toxic hazardous substances and have a significant vapor pressure, so that when processing monomeric diisocyanate this can get into the working atmosphere. Thus, for safety reasons should be low-monomer Systems are worked. However, these polyisocyanates with, for example, uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetrione structures and / or urethane and / or isocyanate-containing reaction products, known as isocyanate prepolymers, have the disadvantage that they have a significantly lower NCO content. Have content as the monomers, so that in the reaction to polyurethanes significantly more isocyanate must be used. In the case of the same molding density, the polyurethane is diluted as a result, ie fewer new polyurethane reactions take place than when monomers are used. Since heat is released by the polyurethane reaction, which further accelerates the reaction, low-monomer systems are usually much slower / less reactive than systems with a high proportion of monomers.

In order to prepare compact, aliphatic polyurethanes, l-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI) is mostly used, which has a certain stiffness due to its cyclohexane ring (US Pat. No. 4,772,639). In order not to use IPDI as a monomer, the only option is to use it in derivatized form as a low-monomer polyisocyanate with, for example, uretdione, isocyanurate and / or allophanate structures and / or as low-monomer isocyanate prepolymer. However, it is known that low monomeric IPDI polyisocyanates with still relatively high NCO contents, e.g. the IPDI trimer (isocyanurate) and the IPDI dimerisate (uretdione) are present at room temperature as a solid or in highly viscous form and these products are thus solvent-free poorly processable. Usually, compact PUR systems are processed in the RIM process (Reaction Injection Molding). For this purpose, both the isocyanate and the polyol component should each have a viscosity of max. 30,000 mPas measured at 20 ° C to allow good mixing and processing at low temperatures.

If one compares the different forms of polyisocyanates with one another, especially the isocyanurate and iminooxadiazinedione or oxadiazinetrione structures and the uretdione structure have a positive effect on the hardness on account of the further ring structure. In contrast, allophanate and biuret polyisocyanates tend to give somewhat softer polyurethanes. The use of derivatives of linear 1,6-diisocyanatohexane (HDI) also has a negative effect on the hardness. However, due to their chemical structure, polyisocyanate compounds of the HDI are significantly less viscous than those of the IPDF.

Thus, it is not surprising that compact, hard polyurethanes are usually produced using an IDPI-isocyanurate / IPDI monomer mixture in a weight ratio of about 30:70 (EP-A 0929586 or WO 2007/078725). However, a disadvantage of these systems is in particular the vapor pressure of the monomeric IPDI contained and the resulting expense of a work-hygienic processing. To avoid this disadvantage, the skilled person would resort to the known low-monomer, aliphatic polyisocyanates. However, neither pure HDI polyisocyanates nor pure IPDI polyisocyanates are suitable for the abovementioned reasons (dependence on reactivity, processability and the necessary achievable hardness). Low-monomer solvent-free blends of derivatives of linear aliphatic diisocyanates such. As HDI, and derivatives of cycloaliphatic diisocyanates, such as. IPDI, are already known for certain selected applications.

Low-monomer mixtures of solid or very highly viscous (> 100,000 mPas / 23 ° C) cycloaliphatic polyisocyanates with low-viscosity linear aliphatic polysiocyanates are known from EP-A 0693512. They are used in combination with solvent-free polyols for the production of abrasion-resistant coatings, in particular for balcony and roof waterproofing.

Solvent-free polyisocyanate mixtures of HDI polyisocyanates and polyisocyanates of cycloaliphatic diisocyanates are also known from EP-A 1484350. Application here is the lightfast coating of decorative parts by combination with special solvent-free polyester polyols having an OH functionality <3. Also in WO 2010/083958 are mixtures of polyisocyanates, prepared from HDI and prepared from cycloaliphatic diisocyanates, application for producing light-fast compact or foamed polyurethanes, in particular for the production of casting resins.

It is an object of the present invention to provide compact, lightfast polyurethane / polyurethane molded parts using an isocyanate and a polyol component, e.g. for the field of application of dashboards, door linings, armrests and brackets in the automotive industry to provide that have a Shore A hardness of at least 70, preferably of at least 75, wherein the viscosity of the isocyanate component max. 30,000 mPas (measured at 20 ° C) should be, as well as a process for their preparation, wherein polyisocyanates are used, which can be processed hygienic so that during processing and curing no volatile components in the ambient atmosphere.

This problem could be solved by providing the polyurethanes or polyurethane ureas described in more detail below and the moldings produced therefrom. Corresponding moldings could surprisingly be obtained from monomer-poor (<0.5% by weight monomer content) aliphatic polyisocyanates having an average NCO functionality of from 2.0 to 3.2 and isocyanate-reactive short and long chain casters.

The present invention provides compact, lightfast polyurethane molded parts with a Shore A hardness (measured according to DIN 53505 at 23 ° C.) of at least 70, particularly preferably with a Shore A hardness (measured according to DIN 53505 at 23 ° C.) of 75 to 85 out ,

- 4 -

A) organic isocyanate compounds having at least two aliphatically bonded isocyanate groups,

B) polyols having an average molecular weight of from 1,000 to 15,000 g mol and an average functionality of from 1.8 to 8 (number of OH groups per molecule), preferably from 2 to 6,

C) Polyols and / or polyamines having a molecular weight of 60-500 g / mol and a functionality (number of OH and / or NH groups of the polyols or polyamines per molecule) of 2 to 8, preferably from 2 to 4 as chain extender / crosslinker,

D) catalysts,

E) optionally further auxiliaries and additives, characterized in that component A) has a content of monomeric diisocyanate of less than 0.5 wt .-%, preferably less than 0.4 wt -%, a viscosity of max. 30,000 mPas (at 20 ° C) (measured according to DIN EN ISO 3219), preferably of max. 25,000 mPas (at 20 ° C), more preferably of max. 20,000 mPas (at 20 ° C) and an average NCO functionality of 2.0 to 3.2, preferably from 2.2 to 3.0, most preferably from 2.2 to <2.5.

The invention is based on the surprising observation that in combination of known solvent-free mixtures of low-monomer low-viscosity polyisocyanates A), in particular prepared from linear aliphatic diisocyanates and cycloaliphatic diisocyanates with polyols B) and polyols and / or polyamines C) lightfast polyurethanes with Shore A hardnesses of at least 70.

Also particularly preferred are compact, lightfast polyurethane molded parts obtainable from mixtures of 35 to 95 wt .-% of at least one polyisocyanate a-1) prepared from at least one linear aliphatic diisocyanate and having an NCO content of 10 to 28 wt .-% and from 5 to 65% by weight of at least one polyisocyanate a-2) prepared from at least one cycloaliphatic diisocyanate and having an NCO content of 10 to 22% by weight as organic isocyanate compounds A), wherein in the polyisocyanate mixture A) at least one of the polyisocyanates a-1) and a-2) has an average NCO functionality of <2.6, preferably <2.5, more preferably <2.4, and is present in an amount of at least 30% by weight, based on A) ,

As polyisocyanate component a-1) it is preferred to use aliphatic polyisocyanates which are low-monomer derivatives of monomeric linearaliphatic diisocyanates i-1). Suitable starting diisocyanates i-1) for these derivatives a-1) are any which can be obtained by phosgenation or by phosgene-free processes, for example by thermal urethane cleavage Diisocyanates of the molecular weight range 140 to 400 with linear aliphatic bound isocyanate groups. As compounds i-1) are suitable for. For example, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (HDI), 2-methyl-l, 5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane, 2.2 , 4- or 2,4,4-trimethyl-l, 6-diisocyanatohexane, 1,10-diisocyanatodecane or any mixtures of such diisocyanates. The derivatives a-1) prepared from the monomeric aliphatic diisocyanates i-1) are prepared by customary known processes, have concentrations of monomeric diisocyanate i-1) of less than 0.5% by weight and contain, for example, uretdione, isocyanurate , Allophanate, biuret, iminooxadiazinedione, oxadiazinetrione and / or carbodiimide structures, as described, for example, in J. Prakt. Chem. 336 (1994) 185-200, DE-A 1 670 666 and EP-A 0 798 299. As polyisocyanates a-1) it is also possible to use urethane and / or allophanate groups, if appropriate, and also reaction products containing isocyanate groups, so-called isocyanate prepolymers. The polyisocyanates a-1) preferably have an isocyanate content of 10 to 28 wt .-%. Preferred but not exclusive isocyanate components a-1) are low-viscosity products based on HDI with a monomer content of <0.5% by weight. Particular preference is given to using HDI polyisocyanates which contain uretdione groups and / or HDI prepolymers.

As polyisocyanate component a-2) it is preferred to use cycloaliphatic polyisocyanates which are low-monomer derivatives of monomeric aliphatic diisocyanates i-2). Suitable starting diisocyanates i-2) for these derivatives a-2) are any by phosgenation or by phosgene-free processes, for example by thermal urethane cleavage, accessible diisocyanates of the molecular weight range 166 to 400 with cycloaliphatic bound isocyanate groups or with Isocyanatomethyl-cycloalkyl structures. As compounds i-2) are suitable for. B. 1,3- and 1,4-diisocyanatocyclohexane, 1,3- and 1,4-bis (isocyanatomethyl) cyclohexane (H ₆ -XDI), 1-isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 4,4'-diisocyanatodicyclohexylmethane (H12-MDI, optionally in admixture with the 2,4'-isomer), 1-isocyanato-1-methyl-4 (3) isocyanato-methylcyclohexane (IMCI), bis (isocyanatomethyl) norbornane (NBDI) or any mixtures of such diisocyanates. The derivatives a-2) prepared from the monomeric aliphatic diisocyanates i-2) are prepared by customary known processes, have concentrations of monomeric diisocyanate i-2) of less than 0.5% by weight and contain, for example, uretdione, isocyanurate , Allophanate and / or carbodiimide structures. As polyisocyanates a-2) it is also possible to use reaction products containing urethane and / or optionally allophanate and isocyanate groups, so-called isocyanate prepolymers. The polyisocyanates a-2) preferably have an isocyanate content of 10 to 22 wt .-%. Preferred but not exclusive isocyanate components a-2) are those based on IPDI or H12-MDI with a Monomer content <0.5 wt .-%. Particular preference is given to using IPDI polyisocyanates which contain allophanate and / or isocyanurate groups.

Component B) has an average hydroxyl functionality of from 1.8 to 8, preferably from 2 to 6, and preferably consists of at least one polyhydroxy polyether having an average molecular weight of from 1,000 to 15,000 g mol, preferably from 2,000 to 13,000 g / mol and / or at least one oligocarbonate polyol having an average molecular weight of 1,000-5,000 g / mol.

Suitable polyhydroxypolyethers are the alkoxylation products known per se from polyurethane chemistry of preferably di- or trifunctional starter molecules or mixtures of such starter molecules. Examples of suitable starter molecules are water, ethylene glycol, diethylene glycol, propylene glycol, trimethylolpropane (TMP), glycerol and sorbitol. Alkylene oxides used for the alkoxylation are in particular propylene oxide (PO) and ethylene oxide (EO), these alkylene oxides being able to be used in any order and / or as a mixture. Furthermore, as component B) it is also possible to use aliphatic oligocarbonate polyols, preferably -diols having an average molecular weight of from 1,000 to 5,000 g / mol, preferably from 1,000 to 2,000 g / mol. Suitable aliphatic oligocarbonate polyols are the per se known transesterification products of monomeric dialkyl carbonates such as dimethyl carbonate, diethyl carbonate etc. with polyols or mixtures of polyols having an OH functionality> 2.0 such as 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-l, 5-pentanediol, 1,12-dodecanediol, cyclohexanedimethanol, trimethylolpropane and / or mixtures of said polyols with lactones, as described by way of example in EP-A 1 404 740 and EP-A 1 518 879. It is also possible to use polyether carbonate polyols, as obtainable, for example, by catalytic reaction of alkylene oxides (epoxides) and carbon dioxide in the presence of H-functional starter substances (see, for example, EP-A 2046861). These polyethercarbonate polyols generally have a functionality of at least 1, preferably from 2 to 8, particularly preferably from 2 to 6 and very particularly preferably from 2 to 4. The molecular weight is preferably from 400 to 10,000 g / mol and more preferably from 500 to 6,000 g / mol. The component C) is preferably difunctional chain extenders having a molecular weight of 60 to 500 g / mol, preferably 60 to 400 g / mol. Preferred chain extenders C) include dihydric alcohols such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, or mixtures of such diols. Also suitable as component C) or as part of component C) are diols having ether groups and having molecular weights of less than 500 g / mol, preferably less than 400 g / mol, as exemplified by propoxylation and / or ethoxylation of divalent starter molecules Type are accessible. Also suitable as chain extender C) are diamines such as ethylenediamine or preferably those with arylalkyl-containing amino groups, such as 1,3-xylylenediamine. Further suitable as component C) are amino alcohols such as, for example, ethanolamine, diethanolamine or triethanolamine. Furthermore, it is also possible to use polycarbonate diols, provided that their molecular weight is below 500 g / mol. Any mixtures of the exemplified chain extenders may also be used. The chain extenders C) are preferably used in amounts of from 2 to 15, preferably from 4 to 12,% by weight, based on the weight of the sum of components B), C), D) and E).

As catalysts D) it is possible to use the known catalysts customary for polyurethane, which are listed, for example, in WO 2008/034884 or EP-A 0929586. These include salts and chelates of tin, zinc, bismuth, iron, mercury as well as tertiary amine compounds. Organotin compounds such as, for example, dimethyltin (IV) didodecylmercaptide, dimethyltin (IV) bis (2-ethylhexylthioglycolate), dimethyltin (IV) dimethyleneisooctylestermercaptide, dimethyltin (IV) didecylmercaptide, dimethyltin (IV) butenyldicarboxylate, dimethyltin (IV) dilaurate and Dimethyltin (IV) di (neo-decylcarboxylate) are preferably used. Preferably, non-fungicidal catalysts should be used.

Optionally with auxiliary and additive E) to be used are compounds of the type known per se. These are the usual and known in the preparation of polyurethanes compounds such. Stabilizers, pigments, fillers or water, which is optionally used in an amount of up to 0.3 wt .-%, based on the weight of component B). Preferably, however, the preparation of the PU is carried out without added water.

Stabilizers are understood as meaning both UV absorbers, antioxidants, free-radical scavengers and foam stabilizers. UV absorbers can be both inorganic compounds such as titanium dioxide, zinc oxide or ceria, as well as organic compounds such as 2-hydroxy-benzophenones, 2- (2-hydroxyphenyl) benzotriazoles, 2- (2-hydroxyphenyl) -1, 3.5 triazines, 2-cyanoacrylates and oxalanilides. Radical scavengers are known to include Hindered Amine Light Stabilizers (HALS), and as antioxidants sterically hindered phenols and / or secondary aromatic amines can be used. Foam stabilizers usually consist of polyether siloxanes or block copolymers of polyoxyalkylenes.

Examples of pigments and fillers are calcium carbonate, graphite, carbon black, titanium dioxide, iron oxide, wollastonite, glass fibers, carbon fibers and / or organic dyes or fillers. _G

Further examples of component E) "auxiliaries and additives" are listed in "Kunststoffhandbuch 7 - Polyurethanes", Becker / Braun, Carl Hanser Verlag, Munich, 1993, 104ff.

The starting components are otherwise used in amounts such that an isocyanate index of 80 to 120, preferably 95 to 105, is maintained. Isocyanate index is the ratio of the number of NCO groups divided by the number of NCO-reactive groups multiplied by 100.

To prepare the PU, components B) to E) are generally combined to form a "polyol component" which is then mixed with the polyisocyanate component A) and reacted in closed forms. Here one uses conventional measuring and metering devices.

The moldings according to the invention are used, for example, as steering wheels or door side panels and instrument panel covers or generally as decorative panels in the car interior. The moldings of the invention are suitable as a panel for dashboards, consoles, panels of doors or shelves in the field of vehicles. Other applications may include: automotive windshield sheathing, window sheathing, solar module sheathing, table edge sheathing, sheathing of metal beams or metal inserts for e.g. Windshots and cables. The moldings may be made by RTM processes or by direct application to other supports of e.g. Polycarbonate, polycarbonate blends, aromatic polyurethanes or other injection-molded plastics are produced in DirectSkinning process.

The temperature of the reaction components (polyisocyanate component A) or "polyol component" consisting of the components B), C), D) and E)) in the preparation of the polyurethanes is generally within the temperature range from 20 to 60 ° C. Die Temperatur The molding tool is generally at 20 to 100 ° C, preferably at 50 to 90 ° C.

The amount of reactive mixture introduced into the mold from components A) to E) is so dimensioned that bulk densities of the moldings of 750 to 1200 kg m ³ , preferably 900 to 1150 kg / m ³ result.

The invention will be explained in more detail with reference to the following examples. Examples

All percentages (compositions) are by weight unless otherwise stated.

The determination of the NCO contents was carried out by titration according to DIN EN ISO 11909, in% by weight.

The NCO functionalities were calculated from GPC measurement (gel permeation chromatogram) and NCO content.

OH numbers were determined titrimetrically in accordance with DIN 53240 T.2.

The residual monomer contents were measured according to DIN EN ISO 10283 by gas chromatography with an internal standard.

The viscosity measurements were carried out with a Physica MCR 51 Rheometer from Anton Paar Germany GmbH (DE) according to DIN EN ISO 3219 (1994), unless stated otherwise. Measurements at different shear rates ensured that the flow behavior of the polyisocyanate mixtures described corresponded to the ideal Newtonian fluids. The specification of the shear rate is therefore deviated from the norm.

Shore hardnesses were measured according to DIN 53505 at 23 ° C. using a Shore hardness tester Zwick 3100 (Zwick, DE).

The tensile test was carried out on a Z020 from Zwick in accordance with DIN 53504 / ISO 37. The tear strength was also measured on a Z020 from Zwick according to DIN ISO 34.

Polyisocyanates a-1)

Polyisocyanate AI):

HDI polyisocyanate containing isocyanurate and uretdione groups was prepared by tributylphosphine-catalyzed oligomerization of HDI on the basis of Example 1a) of EP-A 0 377 177, with the change that no 2,2,4-trimethyl-1,3-pentanediol was used , produced. The reaction was stopped at an NCO content of the crude solution of 42% and unreacted HDI removed by thin film distillation at a temperature of 130 ° C and a pressure of 0.2 mbar. NCO content: 22.7% NCO functionality: 2.2

monomeric HDI: 0.3%

Viscosity (23 ° C): 90 mPas

Polyisocyanate A2): HDI polyisocyanate containing isocyanurate and uretdione groups was prepared by tributylphosphine-catalyzed oligomerization of HDI according to Example 2) of EP-A 0377177. After removal of the excess monomeric HDI by thin-layer distillation, a polyisocyanate was obtained with the following characteristics:

NCO content: 22.5%

NCO functionality: 2.5

monomeric HDI: 0.3%

Viscosity (23 ° C): 170 mPas

Polyisocyanate A3):

An isocyanurate group-containing HDI polyisocyanate A3) was prepared according to EP-A 0330966, Example 11, using 2-ethylhexanol instead of 2-ethyl-1,3-hexanediol as catalyst solvent. After removal of the excess monomeric HDI by means of thin-layer distillation, an HDI polyisocyanate with the following characteristics was obtained:

NCO content: 22.9%

NCO functionality: 3.1

monomeric HDI: 0.1%

Viscosity (23 ° C): 1,200 mPas

Polyisocyanate A4):

7 mol of 1,6-diisocyanatohexane (HDI) and 1 mol of a Polypropylenoxiddiols having an average molecular weight of 400 (OH number = 280) were reacted at 80 ° C until a constant NCO content. Subsequently, the excess of monomeric HDI was removed by thin film distillation at a temperature of 130 ° C and a pressure of about 0.5 mbar.

NCO content: 12.6%

NCO functionality: 2.0

monomeric HDI: 0.2%

Viscosity (23 ° C): 4,250 mPas Polyisocyanates a-2)

Polyisocyanate A5):

4000 g IPDI were degassed at 40 ° C in vacuo and under N2 atmosphere in portions with 25 g of a 5 wt .-% - solution of trimethyl benzylammonium hydroxide in n-butanol / methanol (9: 1) and at 70 ° C reacted until an NCO content of 30% was reached. The reaction was stopped by adding 5 g of a 25 wt .-% - solution of phosphoric acid dibutyl ester in IPDI and stirred at 60 ° C for 1 h. Monomeric IPDI was then separated by distillation by means of a thin-film evaporator at 180-190 ° C. and 0.2 mbar, giving 1600 g of a solid resin (at room temperature) having the following characteristics:

NCO content: 16.7%

NCO functionality: 3.3

monomeric IPDI: 0.35%

Viscosity (140 ° C): 17,000 mPas

Polyisocyanate A6):

10 mol (2222 g) of isophorone diisocyanate (IPDI) were mixed with a mixture of 0.55 mol (40.7 g) of n-butanol and 0.45 mol (39.6 g) of 1-pentanol at 100 ° C until reaching the calculated NCO content of 34.7% implemented. For subsequent trimerization allophanatization, a 5% solution (about 5 g) of trimethyl benzylammonium hydroxide dissolved in 2-ethylhexanol as catalyst was added dropwise at 95 ° C., so that after about 1.5 h an NCO content of the solution of 28.5-29% has been achieved. The reaction was stopped by adding a 25% solution of dibutyl phosphate (about 0.6 g) dissolved in IPDI. The mixture was stirred for 1 h at 120 ° C. Subsequently, the excess of monomeric IPDI was removed by thin-film distillation at a temperature of 150 ° C and a pressure of about 0.5 mbar. A solid resin (at room temperature) with the following characteristics was obtained:

NCO content: 15.0%

NCO functionality: 2,4

monomeric IPDI: 0.4%

Viscosity (100 ° C): 17,000 mPas Polyisocyanate A7):

Isophorone diisocyanate (IPDI) was trimerized according to Example 2 of EP-A0003765 to an NCO content of 31.1%. A mixture of IPDI trimer / IPDI monomer was obtained with the following characteristics: NCO content: 31.1%

NCO functionality: 2.2

Viscosity (23 ° C): 240 mPas

Polyisocyanate I:

Low Viscosity IPDI Trimer / IPDI Monomer Mixture Polyisocyanate A7). Viscosity at 20 ° C according to DIN 53019 approx. 350 mPas, NCO-functionality approx. 2,2

Polyisocyanate II:

Mixture of 50 parts by weight of polyisocyanate A4) and 50 parts by weight of polyisocyanate AI). Viscosity at 20 ° C according to DIN 53019 approx. 420 mPas, NCO-functionality approx. 2.1

Polyisocyanate III: mixture of 60 parts by weight of polyisocyanate A6) and 40 parts by weight of polyisocyanate Al). Viscosity at 20 ° C according to DIN 53019 approx. 24,480 mPas, NCO functionality approx. 2,3

Polyisocyanate IV:

Mixture of 15 parts by weight of polyisocyanate A5), 35 parts by weight of polyisocyanate A3) and 50 parts by weight of polyisocyanate A4). Viscosity at 20 ° C. to DIN 53019 approx. 10,200 mPas, NCO content 16.8%, NCO functionality approx. 2.7.

Polyisocyanate V:

Mixture of 31.5 parts by weight of polyisocyanate A5), 33.5 parts by weight of polyisocyanate A2) and 35 parts by weight of polyisocyanate A3). Viscosity at 20 ° C according to DIN 53019 approx. 11.610 mPas, NCO content 20.8%, NCO functionality approx. 2.9.

polyol:

Polyether polyol having an OH number of 28; prepared by alkoxylation of sorbitol with propylene oxide ethylene oxide (PO / EO) in a weight ratio of 82:18 and predominantly primary OH end groups. Table 1 below describes the components and their amounts used for the preparation of the polyurethane.

compositions

* according to the invention Table 2; properties

* Invention

The mold temperature was 70 ° C in the experiments, the mold size was 100 x 100 x 20 mm ³ . The temperature of the components used was 25 ° C for both the isocyanate and the polyol formulation.

The amount that was poured into the mold was such that the indicated bulk density resulted.

Experiment 1 is a comparative experiment in which a large amount of isocyanate monomer and only IPDI compounds were used. The polyisocyanate I used was very low viscosity, and the molding could be produced within a very short time with a Shore A of 86. A considerable disadvantage, however, was that in experiment 1, large quantities of low molecular weight monomeric aliphatic diisocyanates had to be used which are classified as toxic, sensitizing and irritating working substances and in some cases have a high vapor pressure. The processing of these monomeric diisocyanate-containing mixture required a great safety effort for reasons of work hygiene. In addition, there is a risk that, especially when using a ^

Polyisocyanate excess unreacted monomeric diisocyanate remains in the component for a long time and can evaporate from this slowly.

In contrast, when using the polyisocyanates to be used according to the invention (Examples 3, 4 and 5) and in Comparative Experiment 2, in which low-monomer polyisocyanates were also used, the processing was significantly easier. The polyisocyanates used have a low vapor pressure, so that the ambient air during processing is not contaminated with monomeric diisocyanate. From the finished component can therefore evaporate almost no monomeric diisocyanate. In reactivity, these systems are similar to the system of comparative example; the systems of Comparative Experiment 2 and Experiments 4 and 5 are even more reactive. It can also be seen, however, that the system in Comparative Experiment 2, which is based only on the basis of HDI, only has a fairly low Shore A hardness and thus is relatively soft. Thus, pure HDI polyisocyanates seem to be less suitable for compact, relatively hard polyurethane components based on aliphatic, low-monomer polyisocyanates.

Otherwise, it can be seen that when using the system in Example 3, a better tear propagation resistance is obtained and, when using the system in Example 4, a better tensile strength than the system in Comparative Example 1 is achieved.

Claims

Compact, lightfast polyurethane molded parts with a Shore A hardness (measured according to DIN 53505) of at least 70 available

B) polyols having an average molecular weight of 1,000-15,000 g mol and an average functionality of 1.8 to 8,

C) polyols and / or polyamines having a molecular weight of 60-500 g mol and a functionality of 2 to 8 as chain extender / crosslinker,

D) catalysts,

E) optionally further auxiliaries and additives, characterized in that component A) has a content of monomeric diisocyanate of less than 0.5 wt .-%, a viscosity (measured according to DIN EN ISO 3219) of max. 30,000 mPas (at 20 ° C) and has an average NCO functionality of 2.0 to 3.2.

Compact, lightfast polyurethane molded parts according to claim 1, characterized in that the polyols B) have an average functionality of 2 to 6.

Compact, lightfast polyurethane molded parts according to claim 1, characterized in that the polyols and / or polyamines C) as chain extenders / crosslinkers have a functionality of 2 to 4.

Compact, lightfast polyurethane molded parts according to claim 1, characterized in that component A) has an average NCO functionality of 2.2 to 3.0.

Compact, lightfast polyurethane molded parts according to claim 1, characterized in that the component A) has an average NCO functionality of 2.2 to <2.5.

Compact, lightfast polyurethane molded parts according to claim 1 with a Shore A hardness (measured according to DIN 53505) of 75 to 85.

Compact, lightfast polyurethane molded parts according to one or more of claims 1 to 6, characterized in that the organic isocyanate compounds A) are mixtures of 35 to 95 wt .-% of at least one polyisocyanate a-1) prepared from at least one linear aliphatic diisocyanate and with an NCO content of 10 to 28 wt .-% and from 5 to 65 wt .-% of at least one polyisocyanate a-2) prepared from at least one cycloaliphatic diisocyanate and having an NCO content of 10 to 22 wt .-% and that in the polyisocyanate at least one of the polyisocyanates a-1) and a-2) has an average NCO functionality of <2.6 and in an amount of at least 30% by weight, based on A).

8. Compact, lightfast polyurethane molded parts according to claim 7, characterized in that in the polyisocyanate mixture A) at least one of the polyisocyanates a-1) and a-2) has an average functionality of <2.5.

9. Compact, lightfast polyurethane molded parts according to claim 7, characterized in that in the polyisocyanate mixture A) at least one of the polyisocyanates a-1) and a-2) has an average functionality of <2.4.

10. Use of the moldings according to claims 1 to 7 as a panel for dashboards and consoles, as a lining of doors and shelves in the field of vehicles, as car windscreens, window sheathing, solar module sheathing, table edge sheathing and sheathing of metal or metal inserts.

11. A process for the production of the molded parts according to claims 1 to 7 by IM (Reaction Injection Molding) - method or by direct application of the mixture of the components A) to E) on supports of polycarbonate, polycarbonate blends, aromatic polyurethanes or injection molding Plastics in the DirectSkinning process.